System and method for determining combustion temperature using infrared emissions

Abstract

The present invention relates to a combustion temperature sensor, and, more particularly, to a combustion temperature sensor that measures infrared radiation emitted at several preselected wavelengths from a flame and/or a flame's hot gas at a turbine inlet location and applies the energy signals. to a calculation model to yield temperature.

What is claimed is:  
     
       1. In a system for measuring IR radiation of a flame in a gas turbine having a combustion chamber and a turbine section, the improvement comprising a housing for housing and supporting a lens, an optical fiber, an optical chopper, and a plurality of infrared detectors; said lens for collecting infrared radiation from that portion of a flame nearest to an inlet to the turbine section and focusing said infrared radiation on a first end of said optical fiber, a second end of said optical fiber being held in a fixed relationship to said detectors so that infrared radiation transmitted by said fiber is projected onto a first infrared filter having a first infrared transmission of 2.28 μm (+/−0.005 μm), a second infrared filter having a second infrared transmission of 2.6 μm (+/−0.015 μm), a third infrared filter having a third infrared transmission of 2.7 μm (+/−0.015 μm), and a fourth infrared filter having a fourth infrared transmission of 2.8 μm (+/−0.005 μm), said first infrared filter generating a discrete background infrared radiation wavelength, said second, third and fourth infrared filter each generating a discrete infrared radiation corresponding to CO 2  and H 2 O gas emissions, each said filter directing said infrared radiation wavelength onto an associated detector, and an optical chopper for interrupting the infrared beam at a predetermined frequency before it reaches said first end of said optical fiber. 
     
     
       2. The system as claimed in  claim 1 , further comprising an outer housing at least partially surrounding said housing and defining an air gap therebetween to permit the ingress and egress of fluid within said air gap. 
     
     
       3. The system of  claim 1 , wherein each said filter being positioned adjacent each other and passing only a narrow range of infrared radiation frequencies to its associated detector. 
     
     
       4. The system as claimed in  claim 1 , wherein each said detector produces an electrical signal proportional to said infrared radiation. 
     
     
       5. The system of  claim 1 , wherein said optical fiber is formed of chalcogenide (As 2 S 3 ). 
     
     
       6. The system as claimed in  claim 1 , further comprising a closed-loop cooling system for cooling said detector elements. 
     
     
       7. The system of  claim 1 , wherein the optical chopper operates at a frequency on the order of 65 Hz. 
     
     
       8. The system of  claim 1 , wherein said first end of said optical fiber is positioned in a focal plane of said lens.